package com.gjx.leetcode;

import java.util.LinkedList;
import java.util.Queue;
//116. 填充每个节点的下一个右侧节点指针
//
//
//给定一个完美二叉树，其所有叶子节点都在同一层，每个父节点都有两个子节点。二叉树定义如下：
//
//struct Node {
//  int val;
//  Node *left;
//  Node *right;
//  Node *next;
//}
//填充它的每个 next 指针，让这个指针指向其下一个右侧节点。如果找不到下一个右侧节点，则将 next 指针设置为 NULL。
//
//初始状态下，所有 next 指针都被设置为 NULL。
//
// 
//
//示例：
//
//
//
//输入：{"$id":"1","left":{"$id":"2","left":{"$id":"3","left":null,"next":null,"right":null,"val":4},"next":null,"right":{"$id":"4","left":null,"next":null,"right":null,"val":5},"val":2},"next":null,"right":{"$id":"5","left":{"$id":"6","left":null,"next":null,"right":null,"val":6},"next":null,"right":{"$id":"7","left":null,"next":null,"right":null,"val":7},"val":3},"val":1}
//
//输出：{"$id":"1","left":{"$id":"2","left":{"$id":"3","left":null,"next":{"$id":"4","left":null,"next":{"$id":"5","left":null,"next":{"$id":"6","left":null,"next":null,"right":null,"val":7},"right":null,"val":6},"right":null,"val":5},"right":null,"val":4},"next":{"$id":"7","left":{"$ref":"5"},"next":null,"right":{"$ref":"6"},"val":3},"right":{"$ref":"4"},"val":2},"next":null,"right":{"$ref":"7"},"val":1}
//
//解释：给定二叉树如图 A 所示，你的函数应该填充它的每个 next 指针，以指向其下一个右侧节点，如图 B 所示。
// 
//
//提示：
//
//你只能使用常量级额外空间。
//使用递归解题也符合要求，本题中递归程序占用的栈空间不算做额外的空间复杂度。


public class Solution116 {
	public Node connect(Node root) {
        if (root == null) {
        	return null;
        }
        
        helper(root, null);
        
        return root;
    }
	
	
	private void helper(Node root, Node brother) {
		
		if (root == null) {
			return;
		}
		
		if (root.left != null && root.right != null) {
			root.left.next = root.right;
		}
		
		if (root.right != null && brother != null) {
			root.right.next = brother.left;
		}
		
		helper(root.left, root.right);
		if (brother != null) {
			helper(root.right, brother.left);
		} else {
			helper(root.right, null);
		}
		
	}
	
}
